1. Field of the Invention
The present invention relates generally to an improved data processing system and in particular to using data processing systems for locating radio frequency identification tags in time and space. Still more particularly, the present invention relates using data processing systems to locating radio frequency identification tags in time and space when information is incomplete.
2. Description of the Related Art
Radio frequency identification tags (also known as RFID tags) have been used for years to track the location of objects in time and space. For example, a radio frequency identification tag can be physically attached to an object being used to manufacture an item, or to an article of manufacture itself as the article is being manufactured. The object or article of manufacture moves about the factory via machines, or is carried by hand, during the manufacturing process. Assuming that at least three radio receivers can read the signal produced by the radio frequency identification tag, the exact position of the radio frequency identification tag can be determined at any given time by using triangulation. The process of performing triangulation can be performed by a computer. In this manner, the position of an object in time and space can be determined. This RFID tag technique can also be used to track other objects outside the confines of a manufacturing setting.
However, a problem arises in tracking radio frequency identification tags if only incomplete information is available. For example, if only one or two receivers can detect the signal from the radio frequency identification tag, then triangulating the position of the radio frequency identification tag is impossible.
This problem can arise under many circumstances. For example, an object to which the radio frequency identification tag is attached may move into a zone through which a radio signal of sufficient power cannot be transmitted. In this case, the radio signal may be received by first and second receivers during a first time period, but only second and third receivers during a second time period. However, because at no time could the signal be received by all three receivers, triangulation cannot be used to determine the position of the radio frequency identification tag at any point. In this case, the only information available is that the signal from the radio frequency identification tag could be detected by first and second receivers during the first time period and by the second receiver and a third receiver during the second time period. This situation can also arise under other circumstances, such as when receivers are located far apart from each other relative to the signal strength generated by the radio frequency identification tag.
The above example shows a situation when incomplete information is available to determine a position of a radio frequency identification tag in time and space. Other situations and examples exist in which only incomplete information exists for making this determination.